Research Highlights

Research Highlights
Corn–Soybean Planting Order Could Impact Farm Revenue

Photo: United Soybean Board

By Carol Brown

Many Midwest farmers grow only corn and soybeans. Rotating them each year is common practice to balance nutrient levels and to keep pest and weed pressure low. But do farmers change which crop they plant first — and does this matter?

Typically, farmers favor corn over soybeans to go in the ground first each spring, but there are many decisions to weigh when making this choice. University of Wisconsin professor and State Soybean Specialist Shawn Conley and researcher Spyridon Mourtzinis conducted a study that simulated crop planting order to measure the effect on yield and gross revenue. The study was funded partially by the Wisconsin Soybean Marketing Board.

“There are many decisions associated with planting a crop each year beyond planting date,” explains Conley. “Crop variety and seed maturity, row spacing, seeding rate and management choices like tillage, pest and weed control, all play into corn and soybean production success. There have been studies done on how these affect a farmer’s bottom line, but we haven’t looked at how the order of planting a crop affects revenue.”

Their simplified case study showed that when weather conditions are favorable for early planting, starting with soybeans has a greater positive impact on yield and revenue than planting corn first. But Conley also cautions farmers to consider all the operational decisions that factor into their bottom line and all associated costs.

“The results in this study showed the importance of crop planting order when farmers grow both corn and soybeans in rotation,” says Conley. “But planting order should be decided after considering yield potential of each crop in each field and the specific cropping systems used per field, their associated costs as well as projected crop prices.”

Figure 1. Corn and soybean relative yield response to planting date for typical input systems in a Wisconsin field. To calculate relative yield, the maximum yield of each crop was set at 100% and all other yields were calculated as a percentage of the maximum. Shaded areas show the 95% confidence levels. Source: Conley and Mourtzinis

The research team simulated yields for 310 locations across 26 states based on maturity groups for both corn and soybean. They selected assumptions for each location including soil type, weather conditions and planting dates, which stayed consistent throughout the exercise. They ran two scenarios: planting corn first followed by soybean and planting soybean first followed by corn. They projected yield calculations for planting dates between April 10 and June 15 over five consecutive years. 

Across all years in the Wisconsin location, corn yield remained high and constant until approximately May 1, then yields started to decline sharply. Soybean yield loss also declined after around May 1, but more gradually and the yield percentage remained higher than corn (Figure 1).

“Our results suggest that in the examined site in Wisconsin, soybeans should be prioritized over corn when planting early, up to mid-April,” Conley says. “After that, corn should be the priority to result in greater revenue.”

Figure 2. Day of the year that corn planting should be prioritized over soybean planting for maximum gross farm revenue (corn + soybean acres) between the 110th to the 145th day of the year (yellow to red colors) given four combinations of input systems. Source: Conley and Mourtzinis

For the other 309 simulated fields across the U.S., the dates defining when one crop should be prioritized over the other when planting varied because of cropping and management systems (Figure 2).

Of course, in real-life situations, other management factors and weather play a huge role in which crops should be planted first, but this decision always remains.

“We used the data gathered from trials across the country through many years of collection to be able to create the algorithms to conduct these scenarios,” Conley comments. “And we understand the vast number of variables that a grower faces each year and with each field they farm, but breaking down those variables to simple scenarios can go a long way to help with these elemental decisions.”

Download the fact sheet about this study: Corn and Soybean Planting Order Decisions Impact Farm Gross Revenue. It contains additional details about the study including methods, as well as breakdowns on economics and calculations.

Published: Nov 13, 2023